CYPRJEA. CONUS. 



57 



tracted at the two extremities, has a very narrow aperture, trans- 

 versely wrinkled on both sides; when the animal expands it- 

 self, the mantle extends over the shell and envelopes it entirely 



(jig. 69), which, in the 

 progress of time, pro- 

 duces considerable mo- 

 dification in the colours 

 of the latter ; for, at a 

 certain period, it depo- 

 sits new layers of calca- 

 reous matter, not only 

 Fig. -69. CYPR^EA. around the aperture, but 



also upon the whole external surface of this solid envelope. 



18. Also to this tribe of mollusks belongs the 

 genus CONUS (jig. 70), which differs from all the 

 preceding in the conical form of the shell, which 

 gives the genus its name; a slightly, or not at all 

 projecting spire, forms the base of this cone, and the 

 aperture, which is nearly straight, extends from one 

 end of the shell to the other. 



19. A great number of the shells, the principal 

 characters of which we have briefly noted, are re- 

 markable for the elegance of their form and the 

 beauty of their colours ; the Cones, the porcelain 

 shells (Cypraea), the Volutes, and the Olives especial- 

 ly, are much admired for the brilliance of their mark- CONUS. 

 ings. Many other mollusks of the family of Buccinoides are also 

 worthy of attention on account of the viscid liquid, secreted by 

 the gland placed, as we have already seen in the snails, betwixt 

 the heart and rectum. And in a considerable number of these 

 animals, this humour has the property of changing colour when 

 exposed to the action of air and light, and thus passes from 

 greenish yellow to purple; spread upon stuffs, it imparts to them 

 this rich shade, and appears to be the material employed by the 

 ancients for producing their beautiful purple dyes. Pliny relates 

 that on the shores of Tyre, and many other points along the 

 coasts of the Mediterranean, there are found two genera of shells, 

 called Buccinum and Pvrpura^ both of which furnished d}e for 

 the colours termed purple and conchilian. The first of these 

 mollusks appears to be the Buccinum lapillus, and the second 

 (he Murex brandaris (fig. 64) ; but the quantity of colouring 



Fig. 70. 



1 8. What are the characters of the genus Co'nu? ? (Conus, Latin, a 



19. What animals are supposed to yield the purple dye which was cel- 

 brated among the ancients ? 



2V# 



